Signaling method and system



a 1,624,596 p 1927' R, v. HARTLEY SIGNALING METHOD AND SYSTEM Filed Dec. 24. 1920 ill) Patented Apr. 1'2, 1927.,

UNITED STATES 1,624,596 PATENT OFFICE.

RALPH L. HARTLEY. OI EAST ORAN GE, NEW JERSEY, ASSIGN OR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OI NEW YORK.

SIGNALING METHOD AND SYSTEM.

Application filed December 24, 1920. Serial No. 432,984.

This invention relates to signaling systems and more particularly it relates to jects will be apparent from the detailed.

description hereinafter given.

The preferred embodiment of this invention. by means of which multiplex transmission is obtained. comprises a signaling system in which apparatus, such as telegrilphones, are employed at the transmitting stations for recording the messages and re-transmitting them to the outgoing hue and at the receiving stations for recording the messages and subsequently reproducing them so that they can be impressed on a telephone receiver for example.

The method by which multiplex transmission by means of telegraphone tapes is obtained, consists briefly in recording each message on a separate telegraphoue tape and reproducing shortsegments of each message in turn, the reproductions being eti'ectcd at a velocity as many times greater than that of the velocity of recording as there are messages to be transmitted, thereby permitting all the conversations to be reproduced in a single outgoing circuit without overlapping.

in the mechanism hereinafter described for carrying out this method for the simultaneous transmission of two messages, the telegraphone magnets are stationary. Each tape at the transmitting station moves past its recorder continuously and past its ren'oduccr intermittently. The tape moves by its reproducing magnet with twice the velocity it has past its recording magnet and since means are provided for insuring that when one tape is moving past its recorder the other is at rest and vice versa, it follows that both messages may be trans mitted on the same outgoing line without overlapping. At the receiving station,

similar apparatus are provided except that each tape passes the recorder intermittently and continuously passes its reproducer. Each reproducer may be connected in circuit with a receiving device such as a telephone receiver.

For operating the telegraphones at maximum efliciency the following conditions should be obtained. First, the impedance of each of the recording or reproducing magnets should be substantially equal to the impedance of the line to which it is connected; second, magnetic leakage should be reduced to as low a value as possible; third, the reproducing magnet should be of con siderably higher reluctance than its associated recording magnet; and fourth, it is preferable to employ a broad tape of high coereivity instead of a Wire.

This invention will be better understood by reference to the following detailed description, taken in connection with the accompanying drawings which represent this invention embodied in a multiplex telephone system wherein two messages may be itransmittedsimultaneously over the same Referring to the drawing, 10 is a signal transmission line which terminates at one end in a three limb induction coil 11 and an artificial line or balancing network 12 and terminates at its other end in a three limb induction coil 13 and a balancing network 14. The midpoints of the two windings of transformer 13 included serially in line 10 are connected by leads 15 and 16 to the coils of the reproducing magnets 17 and 18, which magnets are adapted to impress on line 10 amplified currents which have been recorded on the telegraphone tapes 19 and 20 by the two telephone transmitters 21 and 22 respectively. The signaling currents impressed on line 10 by the reproducing magnets 17 and 18 are impressed at the other end of the line by the third winding 25 of the three limb induction coil 11 upon the two recording magnets 26 and 27 whereby the messages are recorded on the telegraphone tapes 28 and 29 and received by the telephone receivers 30 and 31 respectively. Block 33 is intended to represent transmitting apparatus similar to that associated with station A for transmittin signals from station B to station A, an block 34: is intended to represent receiving apparatus for station A similar to the re-' ceiving apparatus for station B. Y

The arrangement of this inventionfi-by; means of which messages impressed on line 10 from telephone transmitters 21 and 22 may be sent out simultaneously over line 10 and received respectively by the two receivers and 31 at station B, may be explained as follows:

- The telegraphone tape 20, on which messages from transmitter 22 are recorded by the recording magnet 35, is adapted to move by the recording magnet continuously and by its reproducing magnet 18 intermittently. This continuous operation of part of the ta e 20 and the intermittent operation of other parts of the tape 20 are obtained by having mounted on a shaft 36, a disk 37 4 net 35.

. leased from engagement wit At the particular instant shown in the" operation of the arrangement, the tape 20 is revented from moving pastthe reproducmg magnet 18 on account of a movable pin 40being held'in a slot of the tape by a cam 41 mounted on shaft 36. In order to store up the amount of tape passed on by disk 37 until the time the tape 1s permitted to move past re roducer 18, a drum 43 is provided which, y means of a suitable spring action, keeps taut a wire or tape 44 which is fastened at one'end to the'shaftof a pulley 45 around which the telegraphone. tape passes. The wire or holding tape 44 should be of considerable len th and, as the telegraphone tape passes the isk 37, the excess portion of the tape may be storedup by the winding up of the wire 44 on drum 43. As soon, however, as cam 41 allows in 40 to be rel the tape 20 by a spring action (not shown), wire 46 by suitable spring action. willbe wound on a drum 47 whereby pulley 48 serves to pull the tape 20 past the reproducing magnet 18 until such a time as cam 41 again causes the insertion of pin 40 in a slot of the telegraphone tape. The spring action of drum 47 should be stronger than thatot drum 43 in order that the pulley 48 will be eliective to pull the telegraphone tape past the reproducing magnet. In order to regulate the speed with which the telegraphone tape asses the reproducing magnet 18, a cam 49 is mounted on shaft 36. This cam 49 has pins mounted on its periphery which are aq qm of Cam 49 for the specific embodi- "ment' shown should be of such a size as to pmnit the tape 20 to be pulled past the re.- producmg magnet 18 at a speed twice the speed the tape is passing the recording magnet 35.

After pin' 40 has been pushed in a slot of the telegraphone tape by cam 41, the motion of the tape past the reproducing magnet 18 is stopped and the excess tape passing the disk 37 is stored up again by the retraction of pulley 45 by drum 43. ,Cam 41 on completing another half cyclewill allow pin 40 to be disengaged again and permit the retraction of pulley 48 to pull the tclegraphone tape past the recording magnet and store the excess tape between the rollers 50 and 51 by the retraction of the 'ulley 48.

It follows, therefore, )y the arrangement above described, that the telegraphone tape 20 is continually passing its recording magnet 35 and is passing its reproducingmagnet only half the time but at twice the speed it passes its recording magnet. 53 represents a suitable magnet for destroying the magnetic record on the tape 20 after it has passed 'the reproducing magnet 18 and before it reaches the recording magnet 35 again. Reproducing magnet 18 will, therefore, impress on line 10, signals from the transmitter 22, but the line 10 will be actually employed for the transmission of the signals only one half the time since when tape 20 is at rest with respect to the reproducing magnet 18, no signaling currents may be impressed on line'lO from the telephone transmitter 22.

The a paratus associated with the telegraphone tape 19 are similar to that associated with the tape 20 except that the cam; for the ,tape 19 maintain tape 19 at rest with respect to its reproducing magnet 17 when tape 20 is passing its reproducing magnet 18, and permits tape 19 to pass its reproducing magnet when tape 20 is at rest with ,respect to its reproducing magnet. To this end, cam 53 is mounted on shaft 36 "e that thepart of its periphery hearing the. pins 54 is at an angle of 180 with the cor responding portion of ram 49. Similarly,

the enlarged portion of cam is 180 from the corresponding portion of cam 41.

The i'epro'clucingniagnets 17 and 18 as shown, are connected serially in line 10 and since means, as above described, are provided for preventing the operation of one reproducing magnet when the other is operated, it follows that the two mes ages from telephone transmitters 21 and 22 are impressed on line 10 without any overlapping. 1

If telephone receiver 31 is the receiver at station B which is desired to receive signals from transmitter 22 of station A, the apparatus associated with telegraphone 29 should be similar to that associated with tape 20 except that the position of the reproducing and recording magnets should be reversed,that is, the apparatusshould be so arranged that the tape 29 passes its recording magnet intermittently and passes its reproducing magnet icontinually. As shown in the drawing, the cam is about in position .to allow the retraction of pin 61, whereby tape 29 may be permitted to start passing recording magnet 27 at the instant pin 40 at station A is retracted to permit the passing of tape 20 past the rcproducing magnet 18. In order to insurethat tapes 2t) and 29 are started and stopped sinniltanemisly, motors 38 and 63 should be s 'nchronized by suitable arrangements, not shown. The. synchronizing apparatus of course should take into account the'actual time of transmis-iion between the transmitting and receiving stations.

As soon as the retraction of pins 40 and 61 occurs, which permits the passing of tape 20 past the reproducing magnet 18 and the passing of tape 29 past the recording magnet 27, the message from telephone transmitter 22 is recorded on tape 29 by the magnet 27 and since the tape 29 is passing its recording magnet at a speed twice the speed it is allowed to pass the reproducing magnet Gl, the excess tape is stored up by. the retraction of pulley 65. The tape 29 which is continually passing reproducing magnet 64 causes the production in the telephone receiver 31, of themessag'e transmitted from transmitter 22 of station A. At the time tape 29 is at rest with respect to the reproducing magnet 27, and the excess tape stored up by pulley (35 is running past the reproducing magnet 64, the pulley 6G is being retracted whereby up between the disk 67 and the roller (58 so that the tape will be ready for the next time the cams allow the tape 29 to pass the recording magnet 27. g

It is to be noted that since tape 29 passes its recording magnet 27 while the tape 20 is passing its reproducing magnet 18, it follows that tape 29 is atrest when tape 19 of station A is passing its reproducing magnet 17 whereby signals from transmitter 21 are impressed on the transmission line 10. It therefore follows that the signals from transmitter 21 are not recorded on the tape 29. The cams associated with the telegraphone tape 28, however. should be so arranged that tape 28 starts to pass its recording magnet 26 at the same time tape 19 starts to pass its reproducing magnet 17. The signals impressed on transmission line 10 by the reproducing magnet 17 will therefore, by the recording magnet. 26 be recorded on the telegraphone tape 28 whereby the associated reproducing magnet 17 is adapted to impress on telephone receiver 30 the signals from telephone transmitter 21.

the. excess tape is stored The above described apparatus for obtaining the simultaneous transmission of two messages over the same transmission line may he obviously employed for the simulshould be moved past its recording magnet intermittently at a velocity as many times greater than that of the velocity of repro- (lucing as there are messages to be received.

In order to secure maximum efficiency of operation of a telegraphone the following conditions should be obtained; first, the impedance of each reproducing or recording magnet should be approximately equal to that of the line with which it is associated, for exa1nple,'reco1'dingmagnet 35 should have an impedance approximatelyequal to the impedance of the battery 71 and the transmitter 22; second, low magnetic leakage for each magnet should be obtained by .havin for exam )le all ma netic aths as nearly closed as possible, and by having no abrupt changes in the cross section of the magnetic circuit at any point; third, the telegraphone tape should be of high coercivity, for example, material such as steel should be employed; fourth, the reluctance of each reproduccr should be high with respect to the reluctance of its associated recorder; fifth, the telegraphone wire should e transmitted. Similarly at the preferably be a broad tape of appreciable thickness and be preferably run at as high a speedas is practicable.

What is claimed is:

1. The method of signaling which comprises periodically transmitting to a signaling line segments of speech signals from a source at a greater speed than received from said source, and periodically and alternately transmitting to said line segments of speech signals from another source at a greater speed than received from said other source whereby the segments of speech signals from both sources are transmitted over said line without overlappin".

2. The method of signaling which comprises producing continuous speech signal records at a fixed rate from a number of sources, and. in. periodically transmi ting signal currents in segments from each of said records over the signaling line at a uniform rate greater than they are recorded on the signal records, said segments being transmitted in a predetern'iined sequence whereby said line is only intermittently cmployed for the transmission of speech signals from any one source.

3. The method of signaling which com prises impressing s eech current signals upon a device, diviting said signals into segments, intermittently transmittin to a line said segments at a greater spee than they were impressed on said device, inipressing other signaling currents upon a second device, dividing said other currents into segments, and intermittently transmitting to said line thescgments of said other signaling currents at a speed greater than they were impressed on said second device, said second signals being impressed on said line at times when said line is not being employed in the transmission of said first signals.

4. The method of signaling from a plurality of sources which comprises recording separately at a certain speed speech signals from each of said sources, and intermittently reproducing segincnts of speech signals from each source at a greater speed thanthe speed of recording in such a manner that all of said signals may be impressed upon a transmission line without overlappin 5. The method of signaling from a pinrality of sources which comprises separately recording at a certain speed the speech current signals from each of said sources, and intermittently reproducing in an outgoing line speech current signals corresponding to each of said sources at a greater speed than the speed of recording, the reproduction of said signals corresponding to each source being performed at times when said line is not responsive to signals from said other sources.

6. The method of signaling which comprises reproducing speech current signals from each of a plurality of sources, impressing the signals from each source upon a device whereby the signals are translated into a form other than that of electric waves, and subsequently translating segments of signals from each of said sources back to the form of electric waves interniittently and at a speed of translation greater than the speed of said first transla tion.

) responding to one of said sources, and intermittently causing another of said records to produce signaling currents corresponding to another source in said transmission line at times when signals corresponding to said first source are not being impressed thereon.

8. The method of im ressing signals from a plurality of indivi' ual sources upon a common transmission line which comprises causing the signaling currents from each source to produce at a desired speed a magnetic record of said signals, subsequently intermittently causing one of said ma 'netic records to produce at a greater speed signaling currents in said line corresponding to one source, and intermittently causing another of said magnet-ic'records to produce signaling currents corresponding to another source 1n said transmission line at times when signals corres onding to said first Source are not being impressed thereon.

9. The method of signaling between a plu rality of individual transmitters simultaneously operated and individual receivers, said transmitters and said receivers being connected by a common transmission line which comprises-intermittently impressing on said line signaling currents from one transmitter, impressing on said line signaling currents from said second transmitter at times when said line is not receiving signals from said first transmitter, and maintaining said receives connected to'said line continuously throughout the period of said signaling but rendering one of said receivers responsive to currents in said line only when signaling currents from said firsttransmitter are being impressed on said line, and rendering a second receiver responsive to currents in said line only when signaling currents from said second transmitter are being impressedon said line.

10. A multiplex 's eeeh signaling system comprising a transmittin station, acreceiving station, and a transmission line therebctween, said transmitting station comprising sources of voice current signals, means for making continuous records of Said signals at a desired speeed, means for intermittently impressing on said line segments of signaling voice'currents produced bysaid continuous records, said segments produced from the different records being impressed alternately on the line and the voice currents comprising the segments being transmitted at a "S eed greater than the speed of recording, sai reeeiving station comprising means for intermittently making records of the received signal segments, receiving devices, and means for-continuously impressing on said devices,

currents produced by said records at the reeeiving station and at a speed corresponding to the speed of recording at said transmitting station.

11. A signaling system comprising a transmitting station, a receiving station, atransmission line connected th'erebetween, said transmitting station comprising a source of signals, means for continuously making a magnetic record of the signals from said 'i'source atva desired s eed, means for causing said magnetic recor to intermittently produce in said linethe signaling currents at a speed greater thanv the speed at which said record was made, said receiving station comprising means for intermittently making a magnetic record of said signaling currents, a receiving device, and means for causing said last mentioned magnetic record to impress continuously on said device the signaling currents at a speed corresponding to the speed at which said first magnetic record was made.

12. In a receiving system, a tape of magnetic material, a Source of current, a recording evice associated with said source and said tape whereby a magnetic record is, produced on said tape corresponding to the currents from said source, a signal line, a r

producing device associated with said tape and said line whereby the magnetic record on said tape varies the current in said line, and means for causing said tape to pass'said recording device continuously and to pass said reproducing device intermittently.

13. In a. receiving systen'i, a line, an endless tape otmagnet-ic.material, a recording device associatedwith said line and said tape whereby a magnetic record of the currents I in said line is made on said tape, a receiving device, a reproducing device associated with said receiving device and said tape whereby the magnetic recordyon said tape varies the current through said receiving device, and meansfor causing said tape to pass said recording device intermittentlyand pass said reproducing device continuously.

-- "14i Ing anutltipl'e'xsignaling system, a plurality of transmitting statlons, a .plu-

ralitv of receiving stations, a common transmission'line therebetween,-each of said transmitting stations comprising anendless tape of magnetic. material, a source' of signals, a recording device associated with said source and said tape whereby the currents from said source produce a ma netic record on said tape, a reproducing evice' associated 'with said line andsaid tape whereby the. currents in sald line are varied in accordance with the magnetic-record of said tape, means for causing said tape to pass said recording device continuously and pass said reproducin device intermittently, said means for can transmitting station being so related to said means for the other transmitting stations that the tape at one transmitting; station passes its reproducing device only when the other tapes are at rest with respect to their reproducing devices, each of said receiving stations comprising a receiver, and means for making each of said receivers individually throughout its entire periphery, said disk being so positioned that said pins cooperate with said slots to produce a continuous movement of said tape, a second of said disks having pins spaced on that fractional portion of its periphery equal to its circumference divided by the number of transmission stations desired to be operated simultaneously, said second disk being so positioned that the pins on the said disk cooperate with the slots in said tape to control the movement of said tape, said recording device being associated with that part of the tape ad acent szud first disk, and said reproducing device being as sociated with that part of'the tape adjacent said second disk; 7

In witness whereof, I hereunto subscribe my name this 18th day of December A. D., 1920.

RALPH V. L. HARTLEY. 

